1. Field of the Invention
The present invention relates to a planner inverted-F antenna (PIFA), and more particularly, to a PIFA having a rib-shaped radiation plate.
2. Description of the Prior Art
The quality of an antenna is very important for a wireless communication system. A desirable installation of a proper and well-designed antenna on the wireless communication device can raise the value of the signal-to-noise ratio (SNR) of wireless signals, and can improve the bit error rate (BER) of the wireless signals.
Along with the development of wireless communication technologies, the integration of its device can be more and more compact. Accordingly, an embedded micro antenna has to be made as compact as possible so that can be successfully embedded into the wireless communication device. For example, a chip antenna and a planner antenna are two of the most popular micro antennas in the market. Both of the micro antennas have the characteristics of low profile and compact size. The planner antenna can be designed to have a variety of design patterns, such as a microstrip antenna, a printed antenna, and a planner inverted-F antenna (PIFA). Since the planner antenna has a strong sense of direction and a compact size and can be installed on a printed circuit board of the wireless communications device, the wireless communications device, with the planner antenna installed, is cheap.
Please refer to FIG. 1, which is a schematic diagram of a PIFA 10 according to the prior art. The PIFA 10 comprises a ground plane 12, a planner radiation plate 14 installed approximately in parallel with the ground plane 12, a feeding line 16 installed on the radiation plate 14, a feeding contact 18 located on an end of the feeding line 16, and a ground contact 20 electrically connected to the ground plane 12.
The PIFA 10 has a voltage standing wave ratio and a return loss changing in close relation with a position (fx,fy) at which the feeding contact 18 feeds the ground plane 12, a width w of the radiation plate 14, and a distance h between the radiation plate 14 and the ground plane 12. Thus, most of the researches of the PIFA 10 focus on the adjustment of the position (fx,fy), the width w, the distance h, or the shape of the radiation plate 14 so as to obtain an optimized receiving quality of the wireless signals.
Since the ground plane 12 and the radiation plate 14 are both thin metal plates of 0.3 mm only, an insulating material such as a sponge is inserted between the ground plane 12 and the radiation plate 14 to prevent the deformation of the radiation plate 14 by gravity or external force such that the distance h and the gain of the PIFA 10 can be constant.
However, the sponge will melt in the environment of high temperature due to the operation of the wireless communications device. In statistics, the sponge can survive one and a half years only. Moreover, since the sponge cannot survive in the high temperature environment, the high temperature reflow processes of a surface mount technology (SMT) or a wave soldering process cannot be utilized to install the PIFA 10 onto a printed circuit board but a soldering process by solder iron after the high temperature reflow process. Therefore, the manufacturing time and the cost are increased.